1. Field of the Invention
This invention relates to the field of ultrasonic scanning for medical applications, particularly devices for providing both imaging and Doppler data.
2. Prior Art
Numerous ultrasonic scanners are commercially available for diagnostic procedures. In one class of the scanners, an imaging display is presented for the operator. The operator selects a point in the imaging display with a cursor. An ultrasound beam is directed to the point and the echoes are processed to obtain the Doppler shift and thereby, a representation of the local blood flow at that point. A major application for these systems is to evaluate the effects of arteriosclerosis in the peripheral vascular system, primarily carotid, femoral and popliteal arteries. Obstructions in the peripheral vascular system result in locally accelerated blood flow and increased turbulence. Possible areas containing plaque within the lumen of vessels can be identified in the imaging data. The increased velocity of the blood through these obstructed areas may then be studied using the Doppler signal. See for example U.S. Pat. No. 4,141,347 issued Feb. 27, 1979 to Green.
It is known in the prior art to rotate a transducer past an acoustic window which is in contact with the body and to obtain data for an imaging display. When the operator locates an area within the imaging display requiring Doppler examination, the imaging transducer is stopped and a Doppler transducer is aimed at the area of interest and Doppler data is obtained. This method, however, does not provide sufficient accuracy of Doppler examination and does not permit simultaneous Doppler and imaging data.
Another prior art system, also having separate imaging and Doppler transducers, permits more precise alignment by providing continuous motion of the imaging transducer while allowing manual positioning of the Doppler transducer. See for example U.S. Pat. No. 4,407,293, issued Oct. 4, 1983 to Suarez. The position of the Doppler transducer in the system is adjusted by means of a knob on the hand-holdable probe. However, such systems may require separate encoders for the imaging transducer and the Doppler transducer in order to permit accurate determination of the position of each transducer. Additionally, these systems are inconvenient to operate because, while one hand of the operator is required to constantly hold the probe in position on the patient, the operator's other hand must be moved back and forth between the control panel of the ultrasound system and the manual positioning knob on the hand-holdable probe.